Photographic printing material



Patented May 11, 1943 rnoroGRAPnIc PRINTING MATERIAL" New Jersey No Drawing. application September 23, 1941, Serial No. 411,977. In Great Britain January 3,

' ment, it has been proposed to coat in layers, or

to mix together, two different silver halide emulsions having different contrasts (gamma). Thus, an emulsion which works hard and is sensitive to blue (such as a silver chloride emulsion) can be mixed with an emulsion which. works soft and is sensitive to green (such as a spectra'lly sensitized silver bromide emulsion). If such a composite emulsion is exposed to light passing through a blue-green filter, the emulsion works normally and is suitable for negatives of normal gradation (contrast). If, however, it is desired to print from a negative with strong contrasts,

8 Claims.

the light which acts upon the emulsion which works hard is cut off by means of a filter permeable only to green, and a normal picture is obtained by means of the emulsion which works soft. If, on the other hand, it is desired to print from a negative with but little contrast, the light which acts upon the emulsion which works soft is cut oil by means of a filter permeable only to blue, and a normal picture is obtained by means of the emulsion which works hard.

A variation of the above process involves thev sensitization of the contrasty chloride emulsion instead of the softer bromide emulsion, to the green portion of the spectrum.

We have now found that advantageous results can be obtained by mixing together silver chloride emulsions of different contrast, the emulsions having difierent contrasts, the emulsions being sensitive to difierent spectral regions, and the emulsion of the lower contrast containing a small amount of silver bromide, i. e. up to about 5% by weight of the silver halide in the emulsion of lower contrast. The image shades given by the two silver halides of substantially the samev effect thereof will be more narly the same over the whole range, than when the emulsions involvedare different. Moreoverfby incorporajting a small amount of silver bromide. in the silver chloride emulsion of lower contrast, the diffusion of sensitizing dyes from the grains of the one emulsion to the grains of the other is marked-,

ly decreased.

It is, accordingly, an object of our invention to provide a photographic printing material which gives various degrees of contrast. A further object is to provide a process for preparing such materials. Other-objects will become apparent hereinafter;

In accordance with one embodiment of our in vention, two silver chloride emulsions of different contrasts and diiferent violet sensitivities are employed, and the harder of these is color sensitized, say to the blue or blue-green, with a sensitizing dye. The violet sensitivities of the two emulsions should b'e'wi dely separated, so that, through a violet filter, the soft component is substantially fully exposed before the'hard emulsion registers. The emulsion of'lower contrast (the soft emulsion) is prepared to contain a small amount of silver bromide, the silver bromide content bein'g not more than about 5% by Weight of the total silverhali de in the emulsion of lower contrast. The following example will serveto illustrate an emulsion prepared in accordance with this embodiment of our invention; 1

Example 1 A hard washed gelatino-silver-cl'iloride de'- veloping-o'ut emulsion was prepared in the usual manner, except that after emulsification, 5-(3- ethyl-2(3) -benzoxazolylidene ethylidene) -3- (nheptyl)-1-phenyl-2 thiohydantoin was added to the emulsion in a concentration of 0.005 g. per 100 g. of silver nitrate used in preparing the emulsion. The emulsion was held at about 45 C. for about 30 minutes after addition of the dye. A soft washed gelatino-silver-chloride developing out emulsion was prepared containing about 3% of silver bromide and about 1% by weight of silver iodide based on theto tal weight ofjsilver halide in the emulsion and having a speed to violet light considerably greater (2 to 10 times) than that of the hardem'ulsion. The two emulsions were then mixed'in equal proportions at C. The mixed em ulsion was then'co'atedt'o desired weight upon a suitablesupport of paper, glass, cellulose derivative or resin and dried 'in the usual manner. Such a mixed emulsion when exposed with violet light works soft for ordinary which cuts out violet light works hard.

In accordance with a further embodiment of our invention, two silver chloride emulsions of different contrasts and diil'erent violet sensitivities are employed, and the harder of, these is sensitized to the green with a sensitizing dye, while the softer emulsion is sensitized to the blue. While the violet sensitivities of the two emulsions should not be too near in practicing this embodiment of our invention, it is less important to have a wide separation in sensitivities than it i in the foregoing embodiment. The emulsion of lower contrast (the soft emulsion) is prepared to contain a small amount of silver bromide, the silver bromide content being not more than about by weight of the total silver halide in the emulsion of lower contrast. The following example will serve to illustrate an emulsion prepared in accordance with thi embodiment of our invention.

Example 2 A hard washed gelatino-silver-chloride developing-out emulsion was prepared in the usual manner, except that after emulsiflcation, 5-(3- ethyl-2(3) -benzoxazolylidene-ethylidene) -3-(-nheptyl)-1-phenyl-2-thiohydantoin was added to the emulsion in a concentration of 0.005 g. per 100 g. of silver nitrate used in preparing the emulsion. The emulsion was held at about 45 C. for about 30 minutes after addition of the dye. A soft washed gelatino-silver-chloride developing-out emulsion was prepared containing about 3% of silver bromide and about 1% by weight of silver iodidebased on the total weight 01' silver halidein the emulsion and having a speed to violet light greater (2 to times) than that of the hard emulsion. After emulsiilcation, 3- (n-heptyl) 5-(l-methyl-z-p-naphthoxazolylidene) -rhodanine was added twenty minutes be fore ripening wa completed, in a concentration 01 0.01 g. per 100 g. or silver nitrate used in preparing the emulsion. The two emulsions were then mixed in equal proportions at C. The mixed emulsion was then coated to desired weight upon a suitable support of paper, glass, cellulose derivative or resin and dried in the usual manner. Such a mixed emulsion when exposed through a yellow filter (Wratten No. 5) works hard and when exposed through a blue filter (Wratten No. 47A) works soft.

Practiced in accordance with any of the embodiments, it is advantageous to employ a quantity of silver bromide in the silver chloride emulsion of lower contrast equal to from about 1% to about 5% of the weight or the total silver halide in the emulsion of lower contrast, although quantities less than 1% give beneficial eflects.

The ratio 01' contrasts between the two emul-- sions which are mixed can be any desired ratio. However, the gradation of the hard emulsion is advantageously at least 2.5 times greater than that of the sort emulsion.

In practicing our invention, the sensitizing dyes employed should be capable of withstanding a digestion at about C. or about one-hall hour, since such a digestion of the emulsion containing the sensitizing dye appears to increase the firmness with which the dyes are adsorbed to the silver chloride. Moreover, most chloride emulsions are usually ripened (digested) in the presence of an acid, such as citric acid or hydrochloric acid, so that the dye should be capable of withstanding the aforesaid digestion in an acid medium. j

exposures and when exposed through a illter What we claim as our invention and desire to secure by Letters Patent of the United States is:

1. A photographic printing material comprising a mixture of two silver chloride emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have different spectral sensitivities, one of the emulsions having a contrast at least 2.5 times greater than that of the other emulsion, the emulsion of lower contrast having a speed to violet light at least twice as great as the speed to violet light of the emulsion of higher contrast, the emulsion of lower contrast containing silver bromide in a concentration equal to not more than about 5 percent by weight of the silver halide in the emulsion of lower contrast.

2. A photographic printing material comprising a mixture or two gelatino-silver-chloride emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have different spectral sensitivities, one of the emulsions having a contrast at least 2.5 times greater than that of the other emulsion, the emulsion of lower contrast having a speed to violet light at least twice as great as the speed to violet light or the emulsion of higher contrast, the emulsion of lower contrast containing silver bromide in a concentration equal to not. more than about .5 percent by weight of the silver halide in the emulsion of lower contrast.

3. A photographic printing material comprising a mixture of two gelatino-silver-chloride developins-out emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have different spectral sensitivities, oneoi the emulsions having a contrast at least 2.5 times greater'than that or other emulsion, the emulsion of lower contrast having a speed to violet light at least twice as great as the speed to violet light of the emulsion 01' higher contrast, the emulsion of lower contrast containing silver bromid in a concentration equal to not more than about 5 percent'by weight of the silver halide in the emulsion of lower contrast.

4. A photographic printing material comprising a mixture or two silver chloride emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have diilerent spectral sensitivities, one of the emulsions having a contrast at least 2.5 times greater than that of the other emulsion, the emulsion of lower contrast having a speed to violet light from two to ten times greater than the speed to violet light of the emulsion of higher contrast, the emulsion of lower contrast containing silver bromide in a concentration equal to from about 1 percent to about 5 percent of the weight of the silver halide in the emulsion of lower contrast.

5. A photographic printing material comprising a. mixture of two gelatino-silver-chloride emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have dliTerent spectral sensitivities, one of the emulsions having a contrast at least 2.5 times greater than that of the other emulsion, the emulsion oi lower contrast having a speed to violet light from two to ten times greater than the speed to violet light of the emulsion of higher contract, the emulsions of lower contrast containing silver bromide in a concentration equal to from about 1 percent to about 5 percent of the weight of the silver halide in the emulsion of lower contrast.

6. A photographic printing material comprising a mixture of two gelatino-silver-chloride developing-out' emulsions at least one of the emulsions containing a sensitizing dye so that the emulsions have different spectral sensitivities, one of the emulsions having a contract at least 2.5 times greater than that of the other emulsion, the emulsions of lower contrast having a speed to violet light from two to ten times greater than the speed to violet light of the emulsion of higher contract, the emulsion of lower contract containing silver bromide in a concentration equal s benzoxazolylidene-ethylidene) 3 -(n-heptyl) l"-[ bromide in a concentration equal-to from about 1 to about 5 percent by weight of the silver halide in the emulsion of lower contrast.

8. A photographic printing material comprising a mixture of two' gelatino:silver-chloride developing-out emulsions one of the emulsions hav ing a contrast at least 2.5 times greater than that of the other emulsions, the emulsion of lower contrast having a speed of violet light from two to tentimes as great as the speed to violet light of the emulsion of higher contrast, the emulsion of higher contrast containing 5-(3-ethyl-2-(3 benzoxazolylidene-ethy1idene) 3 -v(n-heptyl) l phenyl-2-t'hiohydantoin, the emulsion of lowercontrast containing 3-(n-heptyl)-5-(1-methylz-fl-naphthoxazolylidene)t-rhodanine and containing silver bromide in a concentration equal to from about 1 to about 5 percent by weight of the 20 silver halide in the emulsion'of lower contrast.

, EDWARD P. DAVEY.

EDWARD B. KNo'rr. v

phenyl-2-thiohydantoin and containing silver 

